<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.box{
				border: 2px dotted #000;
				display: flex;
				width: 500px;
				flex-direction:column;
			}
			.item{
				background-color: blue;
				font-size: 50px;
				text-align: center;
				vertical-align: middle;
				color: #fff;
				margin: 20px;
			}
		</style>
	</head>
	<body>
		<div class="box">
			<div class="item">
				<iframe width="560" height="315" src="https://mixdrop.is/e/xw1zjd7nhpkkn9" frameborder="0" allowfullscreen></iframe>
			</div>
			<div class="item">b</div>
			<div class="item">c</div>
		</div>
	</body>
</html>